Lubricant compositions

ABSTRACT

THE ANTIOXIDANT PROPERTIES OF LUBRICANTS ARE IMPROVED BY ADDING THERETO AN ANTIOXIDANT AMOUNT OF AN ALKOXYDIARYLAMINE.

United States Patent LUBRICANT COMPOSITIONS Milton Braid, Westmont, NJ., assignor to Mobil Oil Corporation, New York, NY. No Drawing. Filed Nov. 5, 1971, Ser. No. 196,203

Int. Cl. C10m-1/32 US. Cl. 252-515 R 6 Claims ABSTRACT OF THE DISCLOSURE The antioxidantproperties of lubricants are improved byf'a'dding thereto an antioxidantamount of an alkoxydiarylamine.

I BACKGROUND OF THEVDISCLOSURE Field of the invention This invention relates to lubricant compositions having improved stability properties. More particularly the invention relates to lubricants to whichhave been added a small amount of an additive having the ability to reduce oxidative deterioration of suchlubricant.

Discussionof the prior art It is well known that lubricants tend to oxidize when exposed to adverse conditions during storage or actual use. Such use may include, for example,-the lubrication of an internal combustion engine, where oxidation may tend to accelerate greatly at the high temperatures encountered and in the presence of the metals of construction.

The oxidation of a lubricant may result in the loss of lubricating properties, and if such loss is severe enough and if it goes undetected long enough, the machine itself may become totally inoperative. This deterioration may be detected, however, because it is usually accompanied by an increase in acidity or an increase in-viscosity, or both. These can be determined using conventional tests.

Although testing for lubricant breakdown and maintaining elfective lubrication by periodic renewal or exchange of the-lubricant are acceptable, these may also be quite expensive. Thus, the artwhas tried additives which tend to preventior greatly reduce oxidation. One class of wellknown-additives which has been extensively used as antioxidants for lubricants are the'amines, especially the diarylamines.

Another class of-known'a'ntioxidants are the t-alkylsubstituted"diarylamines. U.S;Pat. 3,414,618 discloses that tertiarylalky-substituted 'diphenyl-,L dinaphthyl-, or N- phenyl-naphthylamine may be used as antioxidants for a syntheticlubricant.

No reference is known, however, which teaches the etherified diarylaminesdescribed'hereinafter as lubricant antioxidants. 1/ I SUMMARY oFi-"He INVENTION Inaccordance the ,invention there is provided a lubricant composition comprising a major amount of a 3,781,206 Patented Dec. 25, 1973 wherein Ar and Ar are selected from the group consisting of phenyl, naphthyl, phenanthryl and anthryl, R and R' are alkyls of from 1-20 carbon atoms, and m and n are 0 to 5, with at least one of them being at least 1.

The invention also provides a new and unobvious method for preparing the above-defined compounds which comprises reacting the hydroxy derivative of the abovedefined compound (i.e., where R or R is hydrogen) with an alkyl halide in a dialkyl formamide solvent, or in dimethylsulfoxide or acetonitrile, in the presence of an alkali metal carbonate. 1

DESCRIPTION OF SPECIFIC EMBODIMENTS As stated above, one of the methods for preparing the alkoxy-substituted diarylamines of this invention is be lieved to be novel and unobvious from any known art. The known methods for producing the compounds involve the preparation of the alkali metal derivative of the starting hydroxy diarylamine prior to reaction with the alkyl halide. This is necessary in the known procedures because in the absence of the alkali metal derivative there is a substantial competitive reaction to the alkyl halide with the amine function. By running the reaction in the presence of an alkali metal carbonate and a suitable solvent as disclosed, there is no need to make, as a separate first step, the alkali metal salt of the aminophenol.

The reaction of the aminophenol with alkali metal carbonate (the alkali metal including sodium, lithium, potassium and cesium) is not merely an in situ reaction. It appears that the dimethyl sulfoxide, acrylonitrile or dialkyl formamides, and especially dimethylformamide, have a selective effect for giving etherification, yielding up to 97% of etherified product in the examples illustrated in detail hereinbelow. On the other hand, the same reaction when run in different solvents yields very substantial amounts of N-alkylation rather than etherification.

In running the reaction of the novel process, good product yields can be expected within the range of from about C. to about 200 0., preferably from about to about C. Usually the reaction can be completed in 2 to 3 hours, but may take several hours, e.g. up to 10 or 12, depending upon the temperature and specific reactants employed.

As a general statement, the aminophenol and alkyl halide may be used up to a molar ratio of about 1:15 of the respective reactants, especially at the lower temperatures. Preferably, however, the ratio should be about 1:1. In practicing the process, from about 1 to about 10 equiv alents of carbonate, preferably about 3 equivalents, can be used per equivalent of aminophenol.

The lubricants which may be improved by the alkoxy diarylamines are mineral and synthetic lubricating oils and greases made therefrom. The mineral oils will be understood to embrace not only the parafiinic, but also the naphthenic members. By synthetic oils are meant synthetic hydrocarbons, polyalkylene oxide oils, polyacetals, polysilicones and the like, as well as synthetic ester oils. Of the latter type there may be mentioned those esters made from monohydric alcohols and polycarboxylic acids, such as 2-ethylhexyl azelate and the like, and those made from polyhydric alcohols and aliphatic monocarboxylic acids. Those of this latter group are especially important, and they include esters prepared from the trimethylols, such as the ethane, propane and butane derivatives thereof, 2,2-disubstituted propane-diols and pentaerythritol with aliphatic monocarboxylic acids containing from about 4 to about 20 carbon atoms. Mixtures of such acids may be used to prepare the esters. Preferred in the practice of this invention are the esters prepared from pentaerythritol and a mixture of C -C acids. In making such esters, a generally acceptable product can be made from commercial pentaerythritol containing about 88% of the mono-form and about 12% of the di-form.

The additives of this invention may be used at a concentration of from about 0.005 to about preferably from about 0.1 to about 5% by weight of the lubricant.

Having described the invention in general terms, the following will specifically illustrate its practice. It will be understood that the examples given are merely for illustration and that there is no intention thereby to limit the scope of the invention.

EXAMPLE 1 4-n-octoxydiphenylamine A mixture of 19 g. of 4-hydroxydi'phenylamine, 16 g. of l-chlorooctane and 57.6 g. of anhydrous potassium carbonate in 150 ml. of N,N-dimethylformamide was refiuxed for 6.5 hours. The resulting reaction mixture was cooled below 100 and was poured into a large excess of cold water. The resulting crystalline solids were collected by filtration. There was thus obtained 29.5 g. (97%) of the 4-n-octoxydiphenylamine, melting point 4243.

EXAMPLE 2 Z-methoxydiphenylamine A mixture of 50 g. of 2-ch1orobenzoic acid, 66.1 g. of anhydrous potassium carbonate, 79 g. of 2-methoxyaniline and 300 ml. of diethyleneglycol dimethyl ether was heated to 140 C. To this mixture about 1 g. of copper bronze and about 0.1 g. of copper iodide were added and heating at 140-145" while stirring was continued for about 3 hours. The reaction mixture was cooled to about 100 and poured into water. The aqueous mixture was filtered and the filtrate was acidified with acetic acid, heated to boiling and filtered. There was collected 58 g. (75%) of tan crystalline Z-methoxydiphenylamine-Z'- canboxylic acid, M.P. 171-172.

One hundred seventy one grams of 2-methoxydiphenylamine-2-carboxy1ic acid was heated at 260 C. under a nitrogen atmosphere for 5 hours. 2-Methoxydiphenylamine was distilled from the resulting reaction mixture as a pale yellow oil, boiling point 198-204 at about 6 mm. pressure.

'EXAMPLE 3 4,4'-dioctoxydiphenylamine The reaction mixture was cooled and poured into water. The crude 4,4-dioctoxydiphenylamine (90 g.) which precipitated was collected by filtration. Recrystallization from ethanol afforded the pure dioctoxydiphenylamine as silvery soft flakes, melting point 76-77 C.

EXAMPLE 4' 3-octoxy-4-tert-octyl diphenylamine A mixture of 75 g. of 3-octoxydiphenylamine and 39.2 g. of diisobutylene were heated to obtain a homogeneous solution. 1 g. of anhydrous aluminum chloride was added to the homogeneous solution and the whole was heated at 135 C. for 6 /2 hours. Following this heating period, the unreacted olefin was removed by distillation and the residue was dissolved in ethyl ether, washed with a dilute aqueous potassium hydroxide and finally withv water. After drying, the solvent was removed by distillation. The residue yielded the product boiling '235240 C. at less than 0.1 mm. of Hg pressure.

The following additional products were made in accordance with the methods indicated.

Made by method 0! Example Name Example- 5 4-ethoxy DPA' 2 6... 3-octoxy DPA. 1. 7- 4-0ctoxy DPA. 1 8. 4-oetoxy PAN I 1 9- 4-decoxy PAN. 1 10- dodecoxy DPA.. 1 11 4-dodecoxy DPA- 1 12. 4-octoxy PB 1 13-- -decoxy PBN. 1 14.- 4 oetadecoxy PBN 3 15 3-benzyloxy DPA.. 1 16. -benzyloxy DP 1 17- -dodecenyloxy 1 l8- 4-dodecenyloxy DPA.. 1 19- 4-(2-ethylhexoxy) DPA 1 20. 3-Isopentoxy DP 1 1 23- 4,4'-diisopentoxy DPA 24- N-pheny -1-(2-methoxy) naphthylamin 25-. N-phenyl-l-(4-0ctoxy) naphthylamine. .4 26. N-phenyl-I-(B-octoxy) naphthylamine. 27-- -methoxy AN 2s .-II. 4-ethoxy PAN 1 Diphenylamine. I Phenyl-l-naphthylamine. 8 Phenyl-2-naphthylamine.

EVALUATION OF PRODUCTS Oxidation test The compounds produced in accordance with this invention were blended into a synthetic ester oil ,lubrica'nt (made by reacting pentaerythritol with an equimolar mixture of C and C monocarboxylic acids) and tested in an oxidation test in accordance with'the'following procedure.

A sample of the test composition is heated and air at the rate of about 5 liters per hour is passed through for a period of about 24 hours. Present in the test sample are specimens of iron, copper, aluminum, and lead. The kinematic viscosity is measured at 100 F. before and after treating to give the change inviscosity (percent KV Weight Initial Additive, percent Temp., Initial KV, cs. AKV, Example additive NN ANN at 100 F. percent Sludge N 425 5.9 22s Nil.

..... 450 8.3 585 Trace.

1 2 425 0 1.0 25.72 17 Do. 1 425 0 1.0 25.72 14 Do. 2 450 0 7.6 25.72 191 Light 1 450 0 7.6 25.72 180 Trace.

2.....'-.'....'..': 2 425 0 1. 3 25. 28 24 D0. 1 425 0 3.6 25.28 51 D0. 2 450 0 5.1 25.28 88 D0. 1 450 0 5.6 25.28 95 Light.

3-..--:.:.:-..-: 2 425 0.25 0.87 28.67 19 Nil. 1 425 0.25 0.93 28.67 11 Nil. 2 450 0.25 7.97 28.65 79 Trace. 1 450 0.25 2.43 28.65 111 Do.

4. .::.:.i 2 425 0. 1 1. 28. 85 19 D0. 1 425 0.1 1.47 28.85 13 D0. 2 450 0.1 2.95 28.96 77 Nil.

1 450 0.1 1.97 28.96 2 Nil. 5 4 450 0.3 3.6 26.32 90 Heavy.

2 450 0.3 3.6 26.32 61 Do. 1 450 0.3 5.9 26.32 97 D0.

4 425 0.03 1.25 27.25 46 Ni]. 2 425 0.03 1.27 27.25 Light 1 425 0.03 1.08 27.25 29 D0. 4 450 0.05 1.85 27.25 64 Nil. 2 450 0.05 1.57 27.25 Nil. 1 450 0.05 2.68 27.25 59 Ni].

7 4 425 0.05 1.25 26.84 59 Trace 2 425 0.05 1.07 26.84 32 Nil. 1 425 0.05 1.58 26.84 22 Nil. 4 450 0.05 2.65 26.84 110 Nil. 2 450 0.05 1.87 26.84 69 Nil. 1 450 0.05 2.38 26.84 66 Nil.

8.-. 4 450 0.05 2.65 28.63 63 Nil.

2 450 0.05 1.87 28.63 98 Light 1 450 0.05 1.88 28.63 39 Heavy.

9 2 425 0.05 1.25 27.51 2? Trace 1 425 0.05 1.05 27.51 40 Do. 2 450 0.05 4.75 27.51 Nil. 1 450 0.05 2.07 27.51 195 Heavy.

10 4 425 0. 5 1.05 27.47 46 Light.

2 425 0. 05 1. 27 27. 47 Nil. 1 425 0.05 1.08 27.47 84 Heavy 4 450 0.05 2.05 27.47 68 Nil.

2 450 0.05 2.07 27.47 47 Time. 4 450 0.05 3.48 27.47 100 Do 11 4 425 0.05 1.25 27.14 52 Nil. 2 425 0.05 1.27 27.14 27 Nil. 1 425 0.05 0.78 27. 14 28 Trace 4 450 0.05 1.85 27.14 86 Nil. 2 450 0.05 1.57 27.14 64 Nil. 1 450 0.05 2.38 27. 14 77 Trace.

12 4 425 0.10 1.00 28.70 48 Heavy.

2 425 0. 10 1. 05 28. 70 63 D 1 425 0.10 0.77 28.70 17 Trace 4 450 0.10 1.20 28.70 48 Heavy. 2 450 0.10 0.75 28.70 26 D0. 1 450 0.10 1.07 28.70 29 D0.

13 4 425 0.20 0.60 29.09 24 Moderate;

2 425 0.20 0.70 29.09 23 Heavy. 1 425 0.20 0.75 29.09 14 Moderate:

14 2 425 0.10 1.00 29.00 24 Nil.

2 450 0.10 2.05 29.00 '102 Trace.

15..'. 2 425 0.13 0.87 28.00 11 Moderate;

. 1 425 0.13 1.23 28.00 11 Trace.

2 450 0.13 4.03 2800 56 Moderate. 1 450 0.13 6.06 28.00 123 Trace.

1 425 0.13 3.26 27.70 45 Light. 2 450 0.13 6.03 27.70 117 Moderate: 1 450 0.13 7.56 27.70 114 Trace.

17 2 425 0.13 0.69 27.09 10 Light.

1 v 425 0.13 3.06 27.09 42 Do. 2 450 0.13 4.08 27.09 86 Do. -1 Y 450 0.13 5.56 27.09 109 D0.

1 425 0.13 3.76 25.87 67 Trace. 2 450 0.13 4.23 25.87 98 Light. 1 450 0.13 4.56 25.87 117 D0.

19 2 425 0.05 0.97 26.85 28 Nil. 1 425 0.05 0.74 26.85 19 Nil. 2 450 0.05 1.77 26.84 56 N11. 1 450 0.05 2.48 26.84 60 Nil.

20 2 425 0.05 1.27 26.94 30 Nil. 1 425 0.05 0.98 26.94 17 Nil. 2 450 0.05 1. 97 26.94 63 Nil. 1 450 0.05 3.08 26. 94 52 Nil.

See footnote at end of table.

TABLE-Continued Weight Initial Additive, percent Temp., Initial KV, cs. AKV,

Example additive F NN ANN at 100 F. percent Sludge 21 2 425 0. 05 O. 73 25. 59 29 Nil. 1 425 0. 05 0. 74 25. 59 23 Nil. 2 450 0. 05 2. 47 25. 47 67 Nil. 1 450 0. 05 3. 58 25. 47 87 Nil.

22 2 450 0. 25 1. 65 26. 52 51 Nil. 1 450 0.25 3. 47 26. 52 78 Nil.

23 2 450 0. 13 2. 43 27. 33 54 Nil. 1 450 0. 13 2. 46 27. 33 47 Ni].

24 2 425 0. 13 5. 23 26. 88 74 Trace. 1 425 0. 13 1. 96 26. 88 34 Light. 2 450 0. 13 7. 1 27. 41 152 Nil. 1 450 0. 13 4. 97 27.41 147 Nil.

25 2 0. 13 0. 94 28. 60 13 Ni]. 1 425 0. 13 0. 97 28.60 9 Nil. 2 450 0. 13 2. 74 28. 86 42 Nil. 1 450 0. 13 3. 57 28. 86 80 Nil.

27 2 425 1. 3 27. 69 23 Heavy.

1 425 0 0. 8 27. 69 17 Do. 0. 425 0 1. 1 26. 62 18 D0. 0. 25 425 0 0. 8 26. 62 D0.

28 2 425 0. 1 1. 5 28. 01 27 D0. 1 425 0. 1 0. 4 28. 01 14 Do. 0. 5 425 0. 1 0. 7 26. 96 15 Do. 0. 425 0. 1 0. 7 26.96 19 D0.

l Estimated.

The compounds disclosed herein may be used in con- I claim:

junction with other lubricant additives. When so used, their properties are not adversely affected. The additional additives may include other antioxidants, such as amines, load carrying agents, metal suppressors and the like. The following table summarizes the results obtained using combinations of alkoxy diarylamines and other amines. In all cases, the same lubricant as above was used. All tests were at 450 F. and employed 1% by weight of each of the two additives.

Ini- Initial tial KV, cs. AKV, Additive Ex. NN ANN at 100 F. percent Sludge 0. 1 2. 25 24. 73 60 Nil. 0. 3. 45 27. 90 69 Trace. 0. 1 3. 40 28. 10 9 Light 0. 1 1. 10 29. 98 1 D0. 0. 1 1. 70 27. 18 56 Nil. pl 0. 1 2. 45 27. 41 71 Trace 23 plus DODPA 0. 13 1. 93 27. 82 66 11. 5O

1 Dioctyldiphenylamine. I Phenyl-l-naphthylamine.

others such as phenyl-lor -2-naphthylamine and dinaphthylamine may be used. Broadly, the useful diarylamines are represented by the formula R,,Ar-NI-I-Ar'---R' wherein Ar and Ar are independently selected from the group consisting of phenyl and naphthyl, R and R are hydrogen or (E -C alkyl and x and y are 0 to the available positions on the ring. 75

1. A lubricant composition comprising a major amount of a lubricant and an amount sufficient to improve the oxidation properties thereof a compound of the formula wherein Ar and AR are selected from the group consisting of naphthyl, anthryl and phenanthryl, R and R are benzyl groups or are alkyl groups containing from 1 to about 20 carbon atoms and each m and'n is from 0 to 5, at least one of m and n being at least 1.

2. The composition of claim 1 wherein said compound is present in said composition in an amount of from about 0.005 to about 10% by weight of said lubricant.

3. The composition of claim 1 wherein the lubricant is a lubricating oil or grease.

4. The composition of claim 3 wherein the lubricating oil is a synthetic ester oil.

5. The composition of claim 4 wherein the synthetic ester oil is made from pentaerythritol and an aliphatic monocarboxylic acid containing from 1 to about 20 carbon atoms.

6. The composition of claim 1 additionally having therein a minor amount of diarylamine of the formula wherein Ar and Ar are independently selected from the group consisting of phenyl and naphthyl, R and R are independently selected from the group consisting of hydrogen and C -C alkyl and x and y are 0 to the available positions on the ring. 9

References Cited UNITED STATES PATENTS 2,771,368 11/1956 Thompson 2s2 -s1.s R 3,660,290 5/1972 Schlobohm 2s2-s1.s A 3,368,975 2/1968 Davis 61: a1. 251-515 A FOREIGN PATENTS 1,285,194 1962 France 2s2-s1.s R

WERTEN F. W. BELLAMY, PrimaryExaminer US. (:1. X.R.

my UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO. 3s7 la Dated December 25,

Inventor(s) I MILTON BRAID It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 27, "f0" should be of Column 7, line #7, "ELL/73" should be 26.73

Signed and "sealed this 9th day of Apr 5.]. 19m.

(SEAL) Attest:

EDWARD I'-1.F'LETCHER JR v G MARSHALL DAi-hi Attesting Officer Commissioner of Patents 

